I think there might be a .35 Remington mag in there as well as some others.

Remington 7mm Magnum uses a magnum length action.

Remington 7mm Mag is pretty flexible. You can get 100gr to 195gr Barnes in .284 caliber. Not sure if the 195gr is manufactured anymore. 139gr-175gr is common factory ammunition. To get much heavier bullets than 7mm Mag, you need to get at least a .338 Win Mag. barrel.

I am loading 120gr Nosler ballistics for varmint at 3400fps. Also can load 175gr at ~2800fps for large animals. Covers a lot of territory.

I was considering moving up to a .338 Lapua, but not sure that my Parker Hale can take it. And I think it would be cheaper to go to the new Ruger in .338 Lapua.